Such a rotary sealer is inter alia known from U.S. Pat. No. 6,786,384 B1.
Typically, in addition to the said one support the horn or the booster connected thereto is provided with a further support arranged a multiple of half a wavelength, e.g. half a wavelength of the applied vibrations, from the said one support and is thus arranged in a point with minimum vibration amplitude in the longitudinal direction. In these points with minimum vibration amplitude in the longitudinal direction, the radial displacement reaches its maximum or is close to reaching its maximum when the horn vibrates.
Furthermore, rotary sealers typically comprise an anvil, e.g. an anvil roller, being rotatable in opposite direction of the horn and having a peripheral face adjacent the sealing face of the sealing horn. The part(s) to be sealed—typically of a thermoplastic material—is/are inserted between the sealing face of the horn and the peripheral face of the anvil roller, sealing being provided due to the vibration of the sealing face of the horns and the pressure exerted between the sealing face and the peripheral face of the anvil roller.
As mentioned, maximum radial movements occur in the points with minimum vibration amplitude. Accordingly, it is vital that the supports are resilient. If the supports are not suitably resilient, a large amount of energy is transferred to the hollow shaft and the housing which otherwise would be utilized in the sealing process. Furthermore, increased mechanical wear arises between the supports, if the supports are not adequately resilient. As a result, the rotary sealer operates unevenly with reduced precision and reduced operating life. Additionally, insufficiently resilient supports cause intense heating of the support areas and may at worst cause the supports to be sealed to the hollow shaft.
For sealing heavy materials or sealing at high velocities, a substantial amount of energy, high amplitude and a comparatively high pressure between the sealing face of the horn and the material to be sealed are required. Known rotary sealers do not allow for sealing under the above operating conditions without large amounts of energy being dissipated in the hollow shaft and the housing resulting in energy loss and a risk of sealing the supports to the hollow shaft.